Jacobson Sarah L, Hopper Lydia M
Psychology, City University of New York, Graduate School and University Center, New York, NY, United States of America.
Lester E. Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, Chicago, IL, United States of America.
PeerJ. 2019 Jan 8;7:e6195. doi: 10.7717/peerj.6195. eCollection 2019.
In contrast to reports of wild primates, studies of captive primates' flexibility often reveal conservatism: individuals are unable to switch to new and more efficient strategies when task demands change. We propose that such conservatism might be a result of task design and hypothesize that conservatism might be linked to primates' lack of causal understanding in relation to experimental apparatuses. We investigated if chimpanzees () and western lowland gorillas () would show greater flexibility when presented with a causally-clear task. We presented six chimpanzees and seven gorillas with a clear tube from which they had to remove straws to release a reward. To first evaluate the apes' causal understanding, we recorded the efficiency with which the apes solved the task (i.e., whether they only removed straws below the reward, ignoring redundant ones above it). To further explore how they solved the task, we also recorded the order in which they removed the straws, which allowed us to determine if habitual action sequences emerged. All apes spontaneously solved the task in their first trial and across repeated trials the majority of their solutions were efficient (median = 90.9%), demonstrating their understanding of the puzzle. There was individual variation in the consistency of straw removal patterns exhibited by the apes, but no ape developed an exclusive habit in the order with which they removed the straws, further indicating their causal understanding of the task. Next, we presented the apes with a new configuration of the same task that required the apes to remove fewer straws to obtain the reward. All apes switched to a more efficient straw removal sequence even though their previously-successful, but now less-efficient, solution remained available. We theorize that because the apes understood the causality of the task, they did not form habits and were not conservative.
与野生灵长类动物的相关报道不同，对圈养灵长类动物灵活性的研究往往显示出其保守性：当任务要求发生变化时，个体无法转向新的、更有效的策略。我们认为这种保守性可能是任务设计的结果，并推测保守性可能与灵长类动物对实验装置缺乏因果理解有关。我们调查了黑猩猩（）和西部低地大猩猩（）在面对因果关系明确的任务时是否会表现出更大的灵活性。我们给六只黑猩猩和七只大猩猩展示了一根透明的管子，它们必须从管子中取出吸管才能获得奖励。为了首先评估猿类的因果理解能力，我们记录了猿类解决任务的效率（即它们是否只移除奖励下方的吸管，而忽略上方多余的吸管）。为了进一步探究它们是如何解决任务的，我们还记录了它们移除吸管的顺序，这使我们能够确定是否出现了习惯性动作序列。所有猿类在第一次尝试时都自发地解决了任务，并且在重复试验中，它们的大多数解决方案都是有效的（中位数 = 90.9%），这表明它们理解了这个谜题。猿类在移除吸管模式的一致性方面存在个体差异，但没有一只猿类在移除吸管的顺序上形成排他性习惯，这进一步表明它们对任务的因果理解。接下来，我们给猿类展示了同一任务的新配置，这种配置要求猿类移除更少的吸管就能获得奖励。尽管它们之前成功但现在效率较低的解决方案仍然可行，但所有猿类都转向了更有效的吸管移除顺序。我们推测，因为猿类理解了任务的因果关系，所以它们没有形成习惯，也不保守。
